The present invention is directed to a rotary mine drilling bit for making blast holes in which the parts are separable and replaceable in the field thereby providing a bit in which the part are reusable and consequently provide lower bit costs. In particular, the bit includes bit supporting legs positioned in longitudinally extending slots; releasable connecting means holding the legs in the slots without requiring the connecting means to bear the thrust loads of operating bit.
Various types of roller bits are used for drilling into the earth""s surface. For example, integrally and permanently assembled roller bits are used in the oil and gas industry for drilling wells. Such bits may drill into the earth""s surface as much as several miles and such bits are not taken apart but are generally operated until they are worn out and are then discarded. Similar type bits are used as mine drilling bits for drilling blast holes in which explosives are inserted into the blast holes to break up the formation for collection. Such blast holes are generally shallow, for example, 50 to 100 feet. However, the use of integral or one-piece drilling bit are not readily reparable and as such are expensive. The blast holes are readily available for inspection after digging each blast hole. If parts become worn or broken, they would be available for repair or replacement if suitably constructed with releasably connected parts.
The present invention is directed to a rotary mine drilling bit for making blast holes in which the more likely parts to be broken or worn may be replaced in the field.
Still a further object of the present invention is wherein the rotary mine drilling bit of the present invention includes an integral body having a longitudinal axis and one end of the body includes a connection for attachment to a drill string. A second end of the body includes a plurality of longitudinally extending slots on the periphery of the second end and a transversely extending thrust shoulder is provided on the body intermediate the ends of the body. Transversely extending connecting means is provided between each of the supporting legs and the second end of the body for releasably connecting the legs to the body and one end of the supporting legs is positioned to engage the thrust shoulder for receiving a longitudinal thrust of the body from a drilling string. A roller bit is connected to the second end of each supporting leg.
Yet a still further object of the present invention is wherein the roller bits are releasably connected to each leg.
Still a further object is wherein the slots are formed by first and second longitudinally extending fins extending outwardly from the body on opposite side of each slot. Preferably, the first and second fins extend outwardly in a diverging direction from each other forming diverging shoulders on opposite sides of each slot and the supporting legs include diverging sides for mating with coacting diverging shoulders when the legs are positioned in one of the slots. Preferably, the angle included between first and second fins is approximately 90 degrees.
Yet a further object is wherein each of the legs includes an inside side which is spaced from contact with the body for insuring that the diverging sides of the legs coact and mate securely with the diverging shoulders on opposite sides of each slot.
Yet a still further object of the present invention is wherein the connecting means include one or more bolts for each of the legs connected to the fins and extending through openings in the legs and openings in the fins wherein the openings are larger than the bolts for insuring that the one ends of the supporting legs engage the thrust shoulder whereby the bolts are not required to bear thrust loads.
Still a further object of the present invention is wherein the body includes a longitudinally extending axial opening therethrough and a longitudinal passageway exteriorly of the body positioned between adjacent legs for allowing the removal of debris from the blast hole.
Yet a still further object of the present invention is wherein the bolts are tightened sufficiently to hold the legs in place by friction between adjacent fins.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.